A003486 a(n) = (n^2 + 1)*3^n.

1, 6, 45, 270, 1377, 6318, 26973, 109350, 426465, 1614006, 5963949, 21611934, 77058945, 271034910, 942244893, 3242852982, 11063007297, 37450647270, 125911658925, 420738651054, 1398200544801, 4623476115726

Offset

0,2

References

A. M. Gleason et al., The William Lowell Putnam Mathematical Competition: Problems and Solutions 1938-1964, Math. Assoc. America, 1980, p. 115.

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (9,-27,27).

Formula

G.f.: (1 - 3*x + 18*x^2)/(1-3*x)^3. - Colin Barker, Jan 12 2012

Mathematica

CoefficientList[Series[(1-3*x+18*x^2)/(1-3*x)^3, {x, 0, 30}], x] (* Vincenzo Librandi, Apr 16 2012 *)

Prog

(Magma)[(n^2+1)*3^n: n in [0..25]]; // Vincenzo Librandi, Apr 16 2012

Crossrefs

Sequence in context: A162230 A258350 A258623 * A262415 A297645 A201191

Adjacent sequences: A003483 A003484 A003485 * A003487 A003488 A003489

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved